This invention relates to a surveillance apparatus and, in particular, to a surveillance apparatus to be used in a camera surveillance system.
Present day camera surveillance systems use a variety of surveillance devices to monitor a location. Typical of these surveillance devices are video monitoring devices which employ a camera and lens assembly. This assembly is usually supported by a housing which is fixedly mounted at the location. The housing is often closed off by a dome made of a plastic or other material.
The camera and lens assembly of the surveillance device define a viewing axis along which the assembly views an image or scene at the location. The lens of the camera and lens assembly conveys the viewed image to an image pickup of the camera where it is converted into an electrical signal. This signal is then conveyed to a monitor at a central location for viewing by the camera surveillance system operator.
Typically, the camera and lens assembly in a video surveillance device includes one or more movable parts whose positions control one or more conditions of the assembly. Adjusting mechanisms (e.g., motors, motor drive circuits and gearing arrangements) are further provided for adjusting the positions of the movable parts so as to alter or change the corresponding conditions of the assembly.
A characteristic of the assembly which is controlled in this fashion is the aforementioned assembly viewing axis. Movable mountings which support the assembly in the housing permit the viewing axis to be tilted in a tilt direction(usually the vertical direction) and panned in a panning direction (usually the horizontal direction).
In addition to the pan and tilt conditions of the assembly, other conditions of the assembly controlled by movable parts are various conditions of the lens portion of the assembly. Typical of these conditions are the so-called focus, zoom and iris conditions of the lens assembly.
U.S. Pat. No. 5,801,770 discloses a surveillance apparatus of the above type wherein the surveillance apparatus includes a stationary housing or platform and a further platform which is rotatably mounted to the stationary housing. The camera and lens assembly is pivotably mounted to the rotatable platform. This permits panning of the viewing axis by rotation of the platform and tilting of the viewing axis by pivoting of the camera and lens assembly.
In the system of the ""770 patent, a microprocessor under the control of programming software is disposed on the stationary housing and provides control over a pan motor and a tilt motor which rotate the platform and pivot the camera and lens assembly, respectively. The microprocessor also interfaces with a communications channel which supports bidirectional communication between the surveillance apparatus and the central location.
In this type of system, as above-indicated, the electrical video signal corresponding to the viewed image is conveyed to the central location. At this location, it is supplied to a monitor which recreates and displays the image. Moreover, systems of this type have been further modified so that text material can be included on the monitor with the viewed image. This is accomplished by including a text overlay unit in the apparatus. This unit also under control of the microprocessor and programming software adds menu information and real-time status information, i.e., text information, to the electrical signal corresponding to the viewed image so that the text information is recreated and displayed at the operator monitor along with the video.
In a video surveillance apparatus of the above type, it is often desirable to be able to prevent certain areas of the viewed video image from being recreated and displayed at the monitor at the central location. One proposal for preventing display of these areas, referred to as privacy zones, is to mask the video surveillance apparatus. In particular, non-transparent adhesive tape can be applied to the protective dome of the apparatus to conceal the privacy zones from the field of view.
As can be appreciated, applying tape to the dome of the surveillance apparatus is a tedious and time consuming process. Moreover, the viewed areas of the image adjacent to the taped privacy zones tend to be out-of-focus, reducing the sharpness of the video image. This condition may also require the surveillance apparatus to perform its auto-focus algorithm more frequently than necessary. While baffles may also be used in place of the adhesive tape, they have similar disadvantages.
It is, therefore, an object of the present invention to provide privacy zones in a surveillance apparatus of the above type in a way which avoids the above disadvantages.
It is a further object of the present invention to provide privacy zones in a surveillance apparatus of the above type which are easy to establish and change.
It is an additional object of the present invention to provide privacy zones in a surveillance apparatus of the above type while limiting costs by using existing components.
In accordance with the principles of the present invention, the above and other objectives are realized in a surveillance apparatus of the above-mentioned type by incorporating into the apparatus an image blanking unit. The image blanking unit acts to modify the electrical video signal corresponding to the viewed image so as to partially or totally obscure or blank the image areas or portions corresponding to one or more preselected privacy zones. In accordance with the invention, a microprocessor control unit of the apparatus and software programming of the apparatus are adapted to control the image blanking unit. This control is effected based on pan, tilt and zoom coordinates associated with privacy the zone location.
In the embodiment of the invention to be disclosed hereinafter, a text overlay unit of the surveillance apparatus is used as the image blanking unit. In particular, the text overlay unit is controlled by the microprocessor and software programming to generate a text overlay signal corresponding to blocks of semi or non-transparent characters defining an image corresponding to the privacy zones. When this overlay signal is added to the video signal corresponding to the viewed image, the non-transparent image areas are overlayed on and totally or partially blank the associated viewed image areas. These areas (privacy zones) thus become obscured and are no longer discernible or viewable. In accordance with the invention, these image areas or privacy zones are established based upon defining triangular blanking areas of the image.
In further accord with the invention, the operator at the central location can communicate with the surveillance apparatus to establish the blank image areas. These blank areas are established based on the pan, tilt and zoom information of the surveillance apparatus and are stored as non-transparent text block characters in RAM memory. They are called from RAM memory by the microprocessor and programming software and fed to the text overlay unit which combines the blanking areas with the video image information as the surveillance apparatus views the scene.
In a further aspect of the invention, the surveillance apparatus is also adapted to generate azimuth and elevation information for viewing on the monitor to provide direction of pan and tilt movement to the operator when the image is obscured by the privacy zone blanking.